This invention relates generally to earth anchors and, more particularly, to a socket drive adapter for a solid hub helical earth anchor.
Conventional helical screw anchors were designed as solid steel hubs welded to helical form plates. There are a variety of earth anchors designed for penetration deep into the ground, having a solid central hub with a helical blade there around. The earth engaging end of the central hub can have a ground piercing tip and the opposite end has a means for engaging a drive tool. Often an elongated hub is used to screw the anchor into the ground. Alternatively, an elongated anchor wrench is applied over the solid hub to rotate the anchor. These solid hub designs work well in soft or easy to penetrate soils. However, they do not handle greater rotational forces required to penetrate hard, compacted or rocky soils.
In the 1980's anchors with socket drive designs were developed. Such socket drive designs are disclosed in U.S. Pat. No. 4,334,392 to Dziedzic, U.S. Pat. No. 4,467,575 to Dziedzic, U.S. Pat. No. 4,742,656 to Farmer, and U.S. Pat. No. 4,979,341 to Norman et al. Some of these patents are owned by a common assignee. Present day socket drive anchors used by utilities and others for guying purposes generally have an elongated, solid square shaft with a square type hub, the hub itself must be considerably larger in cross-section than the solid hub designs. One or more helical, outwardly extending, load bearing blades is welded to the hub. An elongated anchor rod is threadedly engaged to the shaft. For installation, an elongated anchor wrench, including a square tubular end section engages the anchor's square tubular hub. The wrench is rotated, which in turn rotates the shaft and blade so that the anchor is screwed into the earth. It will be appreciated that such socket drive earth anchors using a larger drive tube wrench have an increased torque capacity over an anchor that is rotated by the turning of a a relatively slender, solid anchor rod or the like.
There are several disadvantages associated with the socket drive earth anchors. First, the size of the tubular hub required to engage the drive wrench generally dictates the overall size of the central shaft which is encircled by the helical blade. There is a distinct disadvantage in this design in that it is difficult for a hub having a substantial cross-section to penetrate the soil, particularly hard, compacted or rocky soil. Penetration is enhanced by the use of larger, ground piercing lead points. However, the increased torque capacity of the anchor is partially consumed by the need to drive a larger opening in the soil. In effect, the increased torque capacity cannot be fully utilized since part of it is wasted force needed to overcome the soil's resistance to penetration by the larger hub.
Furthermore, solid hub earth anchors can be cast or forged in one piece. In some cases, the sold hub is forged and the helical blade separately welded on. The socket-type anchors, however, usually require more elaborate expensive manufacturing methods.
It would be advantageous, therefore, to have a socket-type earth anchor having a smaller shaft that is simple and less expensive to manufacture, yet capable of accommodating a powerful drive wrench.